#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<math.h>
int main()
{
    int a, b, c, d;
    scanf("%d%d", &a, &b);
    c = (b / 100) - (a / 100);
    d = (b % 100) - (a % 100);
    if (d < 0)
    {
        c--;
        d += 60;
    }
    printf("%.2d:%.2d", c, d);
    return 0;
}